java - 如何计算两个 ArrayList 之间的差异？

Question

我有两个 ArrayList。

ArrayList A 包含:

['2009-05-18','2009-05-19','2009-05-21']

ArrayList B 包含:

['2009-05-18','2009-05-18','2009-05-19','2009-05-19','2009-05-20','2009-05-21','2009-05-21','2009-05-22']

我必须比较 ArrayList A 和 ArrayList B。结果 ArrayList 应该包含 ArrayList A 中不存在的 List。

ArrayList 结果应该是:

['2009-05-20','2009-05-22']

如何比较？

Answer 1

在 Java 中，您可以使用 Collection接口(interface)的removeAll方法。

// Create a couple ArrayList objects and populate them
// with some delicious fruits.
Collection firstList = new ArrayList() {{
    add("apple");
    add("orange");
}};

Collection secondList = new ArrayList() {{
    add("apple");
    add("orange");
    add("banana");
    add("strawberry");
}};

// Show the "before" lists
System.out.println("First List: " + firstList);
System.out.println("Second List: " + secondList);

// Remove all elements in firstList from secondList
secondList.removeAll(firstList);

// Show the "after" list
System.out.println("Result: " + secondList);

上面的代码会产生如下输出:

First List: [apple, orange]
Second List: [apple, orange, banana, strawberry]
Result: [banana, strawberry]